Portable device detects a diabetic biomarker in tears

Researchers have designed a portable sensing device that can detect the elevated levels of a specific protein in the tears of diabetic patients1. The elevated levels of the protein signal

the early onset of diabetic retinopathy (DR), a disorder that affects the retina, the light-sensitive part of the eyes. Currently DR is diagnosed using complex, invasive eye tests. To find a

simple one, the scientists from the Indian Institute of Technology in Guwahati, led by Dipankar Bandyopadhyay, fabricated the device by coating a water-based suspension of gold

nanoparticles with an antibody that is specific to beta-2 microglobulin (B2M), a protein found in tears and urine. The device also has microchannels where the antibody-coated nanoparticles

mix and react with tears containing B2M. The levels of B2M increase in tears, urine, blood serum and brain fluids in various disorders, including diabetes. Tiny drops of tears, when drawn

into the microchannels, reacted with the antibody-coated gold nanoparticles, triggering a colour change. On reacting with B2M in tears, the nanoparticles’ colour changed from dark purple to

pale purple. This reaction, happening under an LED light placed on one side of the device, reduced the intensity of rays emanating from the reaction mix. A light detector, on the other side

of the device, measures such changes in light intensity and generates a digital signal. A signal-processing unit then converts the signal into a readable one, revealing the concentration of

B2M in human tears. This device could also be used to monitor levels of B2M in urine. REFERENCES 1. Maity, S. et al. Microfluidic immunosensor for point-of-care-testing of

beta-2-microglobulin in tear. ACS. Sustain. Chem. Eng. (2020) doi: 10.1021/acssuschemeng.0c00289